Leo satellite communication systems and methods

ABSTRACT

A low earth orbit (LEO) satellite including a processor, a memory, and a communication sub-system. The communication sub-system including: an antenna array and a reconfigurable digital logic processing device. The processor dynamically reconfigures the reconfigurable digital logic processing device to amplify or attenuate transmissions received from one or more directions of interest, or to amplify or attenuate signals transmitted by the antenna array in one or more directions of interest according to the orbital schedule of the LEO satellite.

TECHNICAL FIELD

Embodiments relate to communication systems and methods. In particular, embodiments relate to systems and methods for low earth orbit (LEO) satellite communication with remote terrestrial communication systems.

BACKGROUND

Positioning sensors in remote environments may provide beneficial information in various economic or environmental contexts. For example, in a remote mining operation, information from sensors positioned in remotely located machinery may be beneficial for managing and improving the remote mining operation. Similarly, for a remotely located farm, information from various sensors positioned on livestock or sensors positioned on the ground may be beneficial in managing and planning operations at the remotely located farm.

Access to information from remote environments presents several technical challenges. In remote environments, there may be significant connectivity and power supply issues. Prior sensor networks and gateways may not provide reliable and rich access to information generated by sensors positioned in remote environments because of a lack of connectivity and power. If connectivity is possible, for example via a satellite uplink, then the current and anticipated future cost of using such an uplink is typically prohibitively high for many sensor deployment scenarios. A satellite uplink using a LEO satellite may often have significant limitations of bandwidth and may have limited time windows over which communication is feasible. Further, the size, power supply and thermal dissipation limitation in LEO satellites present additional challenges for communication systems on board the LEO satellite.

It is desired to address or ameliorate one or more shortcomings or disadvantages of prior satellite communication techniques for LEO nano- or micro-satellites, or to at least provide a useful alternative thereto.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

SUMMARY

Some embodiments relate to a low earth orbit (LEO) satellite, the LEO satellite comprising:

-   -   a microsatellite or nanosatellite chassis housing or carrying at         least one processor, a memory accessible to the at least one         processor, the memory storing an orbital schedule of the LEO         satellite, and a communication sub-system accessible to the at         least one processor; the communication sub-system comprising:     -   an antenna array comprising two or more antenna elements;     -   a reconfigurable digital logic processing device in         communication with the antenna array;     -   wherein the at least one processor is in communication with the         reconfigurable digital logic processing device, and     -   wherein the at least one processor is configured to dynamically         reconfigure the reconfigurable digital logic processing device         to perform directional beamforming based on the orbital schedule         by applying different transfer functions to signals         simultaneously received or transmitted by multiple antenna         elements of the antenna array over time.

The microsatellite or nanosatellite chassis may carry the antenna array on any one of the faces of the chassis. The microsatellite or nanosatellite chassis may carry or house the processor, memory and the reconfigurable digital logic processing device as one of its payload components.

A transfer function defines the mathematical operations performed on one or more signals received by the antenna array. The mathematical operations of a transfer function may include mathematical operations to amplify a part of a received signal and/or mathematical operations to attenuate a part of a received signal, for example.

The directional beamforming may be performed using all antenna elements of the antenna array simultaneously. The at least one processor may be further configured to dynamically reconfigure the reconfigurable digital logic processing device to perform directional beam-nulling based on the orbital schedule by applying different transfer functions to signals received and/or transmitted by multiple antenna elements of the antenna array over time.

The directional beamforming and/or beam-nulling may be performed simultaneously across multiple frequency channels. The directional beamforming and/or beam-nulling may be performed simultaneously in multiple different directions.

The antenna array may be a linear array. The antenna array may be disposed along one side of the chassis. The antenna array may be disposed to substantially cover a minor face of the chassis. Each of the antenna elements may include a patch antenna. The antenna array may include at least four antenna elements. Each patch antenna may include a corrugated radiator.

Some embodiments relate to a low earth orbit (LEO) satellite, the LEO satellite comprising: a chassis housing at least one processor, a memory accessible to the at least one processor, the memory storing an orbital schedule of the LEO satellite, and a communication sub-system accessible to the at least one processor; the communication sub-system comprising:

-   -   an antenna array comprising two or more antenna elements;     -   a reconfigurable digital logic processing device in         communication with the antenna array;     -   wherein the at least one processor is in communication with the         reconfigurable digital logic processing device, and     -   wherein the at least one processor is configured to dynamically         reconfigure the reconfigurable digital logic processing device         to: process signals received by the antenna array to amplify         transmissions received from one or more directions of interest         according to an orbital schedule of the LEO satellite, or         amplify signals to be transmitted by the antenna array in or         more directions of interest for transmission according to the         orbital schedule of the LEO satellite; and

the LEO satellite has a mass in the range of 1 kg to 100 kg.

In some embodiments, the chassis has a CubeSat structure and a size from 1 CubeSat unit to 50 CubeSat units, or from 3 CubeSat units to 6, 12, 16 or 24 CubeSat units.

In some embodiments, the chassis comprises a major face, a minor face, the major face having a greater surface area than the minor face; and the antenna array is provided on at least a part of the minor face.

In some embodiments, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to process the signals received by the antenna array to attenuate transmissions received from one or more directions not of interest according to the orbital schedule of the LEO satellite, or attenuate signals transmitted by the antenna array in one or more directions not of interest for transmission according to the orbital schedule of the LEO satellite.

In some embodiments, the orbital schedule data comprises one or more antenna array configuration records, each antenna array configuration record comprising:

an ephemeris record indicating a scheduled position or a portion of a flight path of the LEO satellite in orbit at different times over a period of time; and

array factor coefficients associated with each of the two or more antenna elements defined in relation to the ephemeris record.

The array factor coefficients define the mathematical operations of the transfer function applied to the signals received or transmitted by the antenna array.

In some embodiments, each array factor coefficient is a complex weight comprising a real coefficient value and an imaginary coefficient value.

In some embodiments, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to process the signals received by the antenna array or amplify signals transmitted by the antenna array based on the scheduled position of the LEO satellite and the array factor coefficients as defined in the antenna array configuration record associated with the scheduled position of the LEO satellite.

In some embodiments, the antenna array is a patch antenna array.

The LEO satellite of some embodiments further comprises an analog to digital converter for pre-processing signals before processing by the reconfigurable digital logic processing device. The LEO satellite of some embodiments further comprises a digital to analog converter for processing signals generated by the reconfigurable digital logic processing device for transmission by the antenna array.

The LEO satellite of some embodiments further comprises a signal channeliser for channelising signals before processing by the reconfigurable digital logic processing device. Channelisation allows transmission or reception of multiple messages or multiple series of messages simultaneously or nearly simultaneously over a common radio frequency range/band. Channelisation allows further scaling of the communication between the LEO satellite and remote terrestrial communication systems.

In some embodiments, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to enable the transmission of signals from the antenna array in one or more directions of interest for transmission according to the orbital schedule data.

In some embodiments, the reconfigurable digital logic processing device comprises a Field Programmable Gate Array (FPGA).

In some embodiments, the LEO satellite receives signals from multiple directions of interest. The at least one processor is configured to dynamically reconfigure the reconfigurable digital logic processing device to level amplitudes of signals received from the more than one directions of interest.

In some embodiments, the LEO satellite transmits signals to multiple directions of interest. The at least one processor is configured to dynamically reconfigure the reconfigurable digital logic processing device to level amplitudes of signals transmitted to the multiple directions of interest.

The LEO satellite of some embodiments further comprises one or more variable gain amplifiers (VGAs) in communication with the at least one processor, wherein when the LEO satellite receives signals from multiple directions of interest, the at least one processor configures the one or more VGAs to level amplitudes of signals received from the more than one directions of interest.

The antenna array of some embodiments comprises four or more antenna elements.

Some embodiments relate to a method of communication between at least one LEO satellite and a plurality of terrestrial gateway devices in communication with a plurality of terrestrial sensor devices, the method comprising:

based on the orbital schedule data, the at least one processor dynamically reconfiguring the reconfigurable digital logic processing device to process signals received by the antenna array or to generate and transmit signals through the antenna array;

the antenna array receiving transmissions and making the received transmissions available to the reconfigurable digital logic processing device;

the reconfigurable digital logic processing device processing the received signals to amplify a subset of the received signals corresponding to signals transmitted by one or more of the plurality of terrestrial gateway devices, or

the reconfigurable digital logic processing device feeding to the antenna array signals for transmission in one or more transmission directions corresponding to respective locations of one or more of the plurality of terrestrial gateway devices.

In some embodiments, the method further comprises the communication sub-system processing the amplified subset of received signals to decode information encoded in the subset of received signals.

In some embodiments, the method further comprises the reconfigurable digital logic processing device processing the received signals to attenuate a second subset of the received signals corresponding to signals not of interest received by the antenna array. The received signals corresponding to signals not of interest may relate to known sources of noise or undesirable signals, such as signals originating from terrestrial sources or other satellites.

In some embodiments, the method further comprises the at least one processor dynamically reconfiguring the reconfigurable digital logic processing device to enable the transmission of signals from the antenna array in one or more directions of interest for transmission according to the orbital schedule data.

Some embodiments relate to a method for providing a satellite communication service, comprising providing a LEO satellite of any one of the embodiments as a payload to a satellite launch vehicle.

The method of some embodiments further comprises launching the satellite launch vehicle configured to release the LEO satellite in an orbit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a communication system according to some embodiments;

FIG. 2 is a schematic diagram of a signal processing part of a communication system of a LEO satellite according to some embodiments;

FIG. 3 is schematic diagram of a digital beam forming part of the communication system according to some embodiments;

FIG. 4 is a schematic diagram illustrating signal processing operations performed by a digital logic processing part of the communication system according to some embodiments;

FIG. 5 is a schematic diagram of a radio frequency gateway part of the communication system according to some embodiments;

FIGS. 6, 7, 8, 9 and 10 are graphs illustrating spatial filtering operations performed by the digital logic processing part of the communication system according to some embodiments;

FIG. 11 is a schematic diagram of an antenna array of the communication system according to some embodiments;

FIG. 12 is an example plan view of a patch antenna array of the communication system according to some embodiments;

FIG. 13 is a plan view of an example antenna array element of the antenna array;

FIG. 14 is a further plan view of an example antenna array element of the antenna array;

FIG. 15 is a side cross-section view of the antenna array element shown in FIG. 14 ;

FIG. 16 is a close-up cross-sectional side view of a probe part of the antenna array element of the antenna array according to some embodiments;

FIG. 17 is a plan view of a ground plane of the antenna array element;

FIG. 18 is a perspective view of a chassis for an LEO satellite according to some embodiments;

FIG. 19 is a schematic view of an LEO satellite according to some embodiments;

FIG. 20 is a flowchart of a method of communication between the at least one LEO satellite and the plurality of terrestrial gateway devices; and

FIG. 21 is a flowchart of a method launching a satellite launch vehicle configured to deploy in orbit the LEO satellite.

DETAILED DESCRIPTION

Described embodiments generally relate to LEO satellites for communication. Particular embodiments relate to communication systems for LEO satellite communications. LEO satellites comprise satellites that orbit the earth at an altitude of 2000 km or less. LEO satellites have an orbital period (time to complete an orbit around the earth) of 128 minutes or less, sometimes closer to 90 minutes. The lower altitude and short orbital period of an LEO satellite give it a field of view that is both small in terms of the area of earth covered and the duration of coverage of a particular area. Accordingly, there is a need to make communications between LEO satellites and terrestrial communication systems more efficient to best utilise the limited field of view and the short duration of the field of view over a certain terrestrial area. For example, data gathering by the LEO satellite from terrestrial systems must be performed in around 240 seconds or less from the moment the LEO satellite is in view of the target terrestrial systems that it is scheduled to communicate with. Further, the frequency spectrum available for the communications between LEO satellites and terrestrial communication systems is also limited. The limited frequency spectrum adds further constraints on the communications between LEO satellites and terrestrial communication systems, amplifying the need for efficiency in the communications.

To increase the data gathering capability of the LEO satellite according to embodiments described herein (as compared to conventional LEO satellites), the LEO satellite communication subsystem of the present disclosure uses digital beamforming to form multiple digital beams simultaneously directed in different terrestrial directions to receive and/or transmit data. Some embodiments utilise three or more digital beams formed simultaneously. Such multiple digital beams are formed by a phased antenna array in some embodiments. The multiple digital beams are generally oriented perpendicularly to the flight direction, in azimuth, of the LEO satellite. This allows the creation of terrestrially directed data funnels on each lateral side of the LEO satellite for efficient communication.

Embodiments leverage particular filtering or beamforming signal processing techniques to enable efficient communications between an LEO satellite and terrestrial communication systems. Various embodiments relate to communication systems for satellites, such as LEO satellites, where the communication systems comprise an antenna array and a reconfigurable digital logic processing device (for example a Field Programmable Gate Array (FPGA)). The reconfigurable digital logic processing device is configured to dynamically receive or transmit signals according to the changing position of the LEO satellite in orbit while taking into account the relative position of terrestrial communication systems on earth. The relative position of terrestrial communication systems on earth may be encoded into schedule data stored in a memory of LEO satellite, for example.

In other words, the reconfigurable digital logic processing device allows multiple beams to be formed to transmit and/or receive data in a first set of directions and to then change its configuration to transmit and/or receive data in a second set of directions as the LEO satellite progresses along its orbital path. Such configuration changes can be made up to 20-40 times during each full orbit period around the earth, for example.

The terrestrial communication systems of the embodiments may comprise gateway devices described in PCT Application No. PCT/AU2019/050429 filed 9 May 2019 and titled “Remote LPWAN gateway with backhaul over a high-latency communication system” the contents of which are hereby incorporated by reference. Such gateway devices may have limited uplink power and so efficient communication with the LEO satellite is important in order to be able to conserve power and maximise data transmission.

LEO satellites orbit the earth at an altitude of 2000 km or less. Launching satellites involves significant costs and the costs of launching are significantly higher for LEO satellites with greater mass. Accordingly, the mass of a LEO satellite is often limited by the costs of launching the LEO satellite into orbit. LEO satellites are often powered by solar cells backed by one or more batteries. Because of the mass limitation on satellites, the capacity to generate power by the solar cells is also limited. The availability of solar power is also constrained by the position of the satellite in its orbit and the exposure to solar power available to the satellite as it orbits the earth. This in turn limits the power available to the various electronic components of the LEO satellite. The power limitations impose restrictions on the nature and number of electronic components that may be incorporated in a LEO satellite.

LEO satellites of some embodiments may comprise a chassis for housing the various electronic and communication components of the LEO satellite. The chassis may enable the efficient utilisation of space and efficient thermal dissipation. In some embodiments, the chassis may be in the form of a CubeSat. A CubeSat comprises a structural framework that comprises one or more cubic structural units. Each cubic structural unit may be in the form of a cube with approximate dimensions of 10 cm×10 cm×10 cm. Various cubic structural units may be aggregated to form a CubeSat structure for the LEO Satellite 110. The size of a CubeSat structure may be represented by the number of cubic structural units comprised in the CubeS at. For example, a CubeSat comprising two cubic structural units may be described as a 2U CubeSat unit satellite.

LEO satellites also have a limited capacity to radiate thermal power to cool down the various components of the satellite that generate heat. Some embodiments may comprise a 6 CubeSat units (6U) LEO satellite (a satellite with dimensions of around 10×20×30 cm or around 12×24×36 cm) structural design and/or framework. The 6 CubeSat unit LEO satellite may receive on average 50-60 W of power per orbit from its solar cell array. Average per-orbit thermal dissipation capability may be approximately 40-45 W. In example embodiments, a 6U nanosatellite operating in S-band frequencies may have a linear array of four antennae. Such an array allows the formation of 4 independent digital beams in azimuth. This gives the potential to double the data gathering capability of LEO satellites when compared with conventional LEO satellites that do not use digital beam-forming. If the antenna array included 8 antenna elements, then such an array could potentially quadruple the data gathering capacity relative to conventional LEO satellites. This is because the antenna array according to embodiments described herein can allow multiple beams to be formed with the same frequency simultaneously.

In some embodiments, the various power-consuming components may be turned on or off to manage the overall consumption of power and the need for thermal dissipation by the satellite. LEO satellites may keep track of their position using a GPS signal receiver 119 fitted on the LEO satellite. In some embodiments, LEO satellites may comprise an orbit propagator program provided in a memory on the LEO satellite. The orbit propagator program may be executable by a processor on board the LEO satellite to determine a position of the LEO satellite at any instance of time, with information regarding acceleration and initial velocity. Using the position information available, the LEO satellite may adaptively turn on or off the various power-consuming components to manage the overall consumption of power and the need for thermal dissipation by the satellite. Some embodiments may comprise a LEO satellite of a size from 1 CubeSat units to 50 CubeSat units. Some embodiments may comprise a LEO satellite of a size from 3 CubeS at units to 48 CubeS at units. For example, the size may be 3U, 4U, 5U, 6U, 8U, 9U, 10U, 12U, 16U, 20U, 24U, 32U, or 48U.

The various components within the LEO satellite may have different requirements for thermal dissipation. Some components may generate more heat in comparison to the rest of the components. In some embodiments, the components generating more heat may be located closer to the chassis (i.e. an outer frame) of the LEO satellite to improve thermal dissipation. Components requiring a lower rate of thermal dissipation may be placed away from the chassis. In some embodiments, thermal straps may be used to improve thermal dissipation. Thermal straps may assist in conducting heating from within the LEO Satellite to its chassis. In particular, components positioned away from the chassis may be provided with heat straps to conduct heat away from the components.

The mass of the LEO satellite of various embodiments may be within a range of 1 kg to 100 kg, 10 kg to 50 kg, or 10 kg to 100 kg, for example. The mass of the LEO satellite of various embodiments may be within a range of 10 kg to 30 kg, for example. Example masses further include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 and 50 kg. A satellite with a mass between 10 kg to 100 kg may be referred to as a microsatellite. A satellite with a mass between 1 kg to 10 kg may be referred to as a nanosatellite.

Spatial filtering as described herein comprises signal processing techniques for focusing the reception or transmission of a wireless signal arriving from or directed to a particular direction of interest or multiple directions of interest simultaneously, such as a terrestrial area of around 100 km² or more. For example, the terrestrial area may be around 200 km². The field of view of the LEO satellite according to described embodiments can be logically segmented into sub-areas, where each sub-area is serviced by one of the multiple beams as described herein. Spatial filtering may also comprise processing received wireless signals to attenuate signals not of interest received from a particular direction (beam nulling). Spatial filtering may also comprise attenuating signals transmitted in one or more directions not of interest. Spatial filtering may provide the LEO satellite the capability to avoid interference with other communication systems and meet any regulatory requirements associated with the operation of the LEO Satellite. Spatial filtering relies on processing signals received by or transmitted by an antenna array in a specific manner to impose constructive or destructive interference or a combination of both constructive and destructive interference to the signals depending on the needs of the communication system at a particular time and location. The combination of constructive and destructive signal interference may be a linear combination resulting from the arrangement of the phased linear antenna array.

The focused spatial filtering is configured to amplify signals from some directions and/or attenuate signals from other directions. For the amplification of received or transmitted signals, the spatial filtering acts to shape the gain of the antenna in selected directions to resemble a “beam” in directions of relatively high gain. This spatial filtering for amplification can therefore also be referred to as beam-forming. For the attenuation of received or transmitted signals, the spatial filtering acts to shape the gain of the antenna array in selected directions to have a signal attenuation effect in the directions of particularly unwanted (i.e. undesirably interferential) ground emitter or receiver signals. This spatial filtering for attenuation can therefore also be referred to as beam-nulling.

Embodiments rely on communication protocols that are designed for low power consumption. The terrestrial communication systems transmitting signals to the LEO satellite may be located in remote locations where power supply or availability thereof may be limited. The communication protocols employed by the terrestrial communication systems may be specifically selected to reduce the power consumption in transmission, reception and processing of the signals in the LEO satellite. Such communication protocols include, for example, spread spectrum based protocols, including chirp spread spectrum based protocols such as LoRa™ (Long Range).

FIG. 1 is a block diagram of an LEO satellite communication system 100 according to some embodiments. The LEO communication system 100 comprises both terrestrial and satellite components that are configured to communicate with each other to provide a communication service. The LEO communication system 100 comprises one or more LEO Satellites 110; one or more remote terrestrial communication systems 120, and at least one ground station 130 in communication with a network 150 through which a client device 140 may interact with the communication system 100. One goal of the communication system 100 is to make the data gathered by the remote terrestrial communication system 120 readily available (although at high latency) to the client device 140, while dealing with the communication constraints of conveying information from remote locations through the LEO satellite 110 to the client device 140.

The remote terrestrial communication system 120 comprises a sensor device network 122 that may be configured to wirelessly communicate with a terrestrial gateway 121, for example. The sensor device network 122 may comprise several or many sensor devices located in a remote area where conventional communication networks, such as the internet or cellular networks, may not be available, for example. Such remote areas may include mines, remote agricultural land, remote scientific research stations, for example. The sensor devices may be configured to sense various environmental conditions, the status of machinery or may be used to track the movement of cattle, for example. The sensor devices network 122 may extend over an area of approximately 700 km², for example. The terrestrial gateway device 121 receives and stores information transmitted by the sensor devices of the sensor device network 122. The terrestrial gateway device 121 also serves as an information relay device between devices in the sensor device network 122 and the LEO satellite 110.

The LEO Satellite 110 comprises a communication system comprising an antenna array 117, a radio frequency front end 115, a digital logic processing device 114, a processor 112, a memory 113 in communication with the processor 112, and a data handling subsystem 116. The LEO satellite 110 also comprises a power management subsystem 111.

The antenna array 117 comprises two or more antenna elements, each antenna element being an independent antenna capable of receiving or transmitting or both receiving and transmitting radio waves or signals. The multiple antenna elements enable spatial filtering capabilities of the communication system of the LEO satellite 110.

The LEO satellite 110 also comprises a radio frequency front end 115 that performs pre-processing of signals received by the antenna array 117 or processing of signals provided to the antenna array 117 for transmission. The processing may comprise conversion of analogue signals to digital signals or vice versa, channelization of signals, and selection or rejection of particular frequency bands of signals, for example.

The reconfigurable digital logic processing device 114 comprises a matrix of configurable logic blocks (CLBs) connected via programmable interconnects. The reconfigurable digital logic processing device 114 may be dynamically reprogrammed to provide desired application or functionality required to provide a communication service through the communication system 100. The CLBs may be reconfigured to implement various digital logic processing capabilities. The CLBs may be configured to operate in cooperation with each other by appropriately programming the interconnects to implement complex logical operations. Advantageously, the reconfigurable digital logic processing device 114 may be reconfigured dynamically to account for changes in the location of the LEO satellite during orbit and consequential changes in the need for spatial filtering to be performed by the communication system of the LEO satellite. In some embodiments, the reconfigurable digital logic processing device 114 may be or include a field-programmable gate array (FPGA).

The LEO satellite 110 also comprises at least one processor 112 that is in communication with a memory 113 and the reconfigurable digital logic processing device 114. The processor 112 has the capability to reconfigure the reconfigurable digital logic processing device 114 according to instructions and data stored in the memory 113. In some embodiments, the LEO satellite 110 may receive commands or instructions from ground station 130 over the link 170. The commands may include instructions to reconfigure the reconfigurable digital logic processing device 114 to meet changing communication requirements between the LEO satellite 110 and one or more remote terrestrial communication systems 120. The capability to reconfigure the reconfigurable digital logic processing device 114 while the LEO satellite 110 is in orbit provides significant flexibility in providing a satellite communication service using described embodiments.

Memory 113 comprises orbital schedule data 118 relating to the LEO satellite 110. Orbital schedule data 118 includes data relating to the scheduled position of the LEO satellite 110 over time with respect to the earth and the various remote terrestrial communication systems 120 as the LEO satellite 110 traverses its orbit. The orbital schedule data 118 also comprises antenna array configuration records that reference an ephemeris record (stored in memory 113) indicating a scheduled position of the LEO satellite 110 in orbit over a period of time, together with array factor coefficients or weights associated with each antenna element defined in relation to the ephemeris record. The array factor coefficients or weights associated with each antenna element (at a particular time) define the mathematical operations to be performed by the reconfigurable digital logic processing device 114 to process the signals received by each antenna element or process signals provided to each antenna element for transmission. The array factor coefficients or weights are complex numbers comprising a real coefficient and an imaginary coefficient. The mathematical operations performed by the reconfigurable digital logic processing device 114 using the array factor coefficients or weights are explained further below with reference to FIG. 4 .

The at least one processor 112 is configured to execute software program code stored in memory 113 to periodically check the current scheduled orbital position and/or the actual determined orbital position of the LEO satellite 110 and then access the orbital schedule data associated with the current (determined) orbital position to determine the array factor coefficients to be provided to the reconfigurable digital logic processing device 114 for signal transmission and/or reception over a next (succeeding) time period. The resetting of the array factor coefficients (and thus redirection of digitally formed beams or nulled beams) can happen frequently according to the ephemeris data corresponding to the determined position of the LEO satellite 110. This means that, during a pass of the LEO satellite 110 over a particular terrestrial area, the array factor coefficients can be reset multiple times in a pass-over period (e.g. 200-250 seconds, optionally around 240 seconds) while the LEO satellite is in range of that particular area. Resetting the array factor coefficients multiple times in a pass-over period for a particular area causes the one or multiple formed or nulled beams of the LEO satellite 110 to be angularly adjusted to account for the satellite movement relative to the particular area. This allows the formed or nulled beams of the satellite to be adjusted to better track and target the particular terrestrial area for improved communication efficiency. In some embodiments, the array factor coefficients can be set according to the ephemeris data for a pass over a known terrestrial area (containing a field of target devices for communication) and the array factor coefficients are maintained for a scheduled time (e.g. the entire pass-over period for that target terrestrial area) while the digitally formed or nulled beams pass over that area. The array factor coefficients can then be reset according to the ephemeris data for the next target terrestrial area that the LEO satellite is scheduled to pass over.

Ground station 130 is a terrestrial radio station designed for receiving and transmitting signals or radio waves from each of the LEO satellites 110. Ground station 130 comprises suitable antennas to communicate with the LEO satellites 110 and suitable network interface components to convey data received from the LEO satellites 110 to a network 150. Network 150 may be or include a data network, such as the Internet, over which the client device 140 may receive or access the data received by the ground station 130. The client device 140 may be a computer server or an end user computing device such as a desktop, laptop, smartphone or tablet, for example.

FIG. 2 is a schematic diagram of a part 200 of the communication system of a LEO satellite 110. FIG. 2 illustrates parts of the RF front end 115 and the reconfigurable digital logic processing device 114. In the exemplary embodiment of FIG. 2 , the antenna array 117 has four elements. However, embodiments contemplate more than four antenna elements. For example, the antenna array may include 5, 6, 7, 8, 9, 10, 12, 15, 20 or more antenna elements. In described embodiments, a minimum of two antenna elements is required to perform the described digital beamforming.

Signals received by each antenna element pass through a band pass filter 210 that removes signals received at frequencies that are not of interest for the LEO satellite 110. In some embodiments, the band pass filter may allow signals of frequencies between about 2170 MHz and about 2200 MHz to pass through, for example. Subsequently, the received signals pass through a radio frequency (RF) amplifier 220. The RF amplifier front-end may provide a total gain in the range of 40 to 60 dB, for example, as additional amplification can be provided in the Intermediary Frequency (IF) stage (228 to 242). The RF amplifier in combination with other components (including the input filter) processing the RF signal may have a noise figure lower than 2 dB from the antenna port, for example.

The radio frequency amplifier 220 increases the sensitivity of the receiver by amplifying weak signals without contaminating them with noise so that they can stay above the noise level in succeeding stages. The RF front end 115 comprises a local oscillator 280 that generates a local RF signal at an offset from the signal received by the antenna array 117. The local RF signal in some embodiments may have a frequency in the range of 1000 to 1200 MHz, for example.

In some embodiments, the local RF signal may have a frequency in C-band (4.5-6 GHz) or in Ku-band (13 to 14.5 GHz) or in Ka-band (27.5 to 31 GHz), for example.

A splitter 280 splits the local RF signal into four different split local RF signals. Each of the split local RF signals are mixed with the signals received by each of the antenna array elements by mixers 225 to generate a mixed phase and amplitude synchronous intermediate frequency signal (MIF1) for all the array elements 117 a to 117 n. The MIF1 signal may have a range of frequencies between 750 to 950 MHz, for example. The MIF1 frequency has a lower frequency than the frequency of the signal received by the antenna array 117 and is more conveniently processed by the rest of the components of the RF front end 115. The components necessary to process signals at lower frequencies are less sophisticated, less expensive and often more power efficient. Further, the antenna array 117 may receive signals at different frequencies. Converting the various signals received by the antenna array 117 to the MIF1 signals simplifies the processing of all the received signals by the rest of the components of the RF front end 115.

The MIF1 signal is subsequently passed through band pass filters 230 to generate an intermediate frequency signal (IF1). In some embodiments, the band pass filter 230 may retain signals within the frequency range of 900 MHz to 930 MHz, for example. In some embodiments, a signal conditioning unit, such as muRata™ SF2098H, may be used to implement the band pass filters 230. The IF1 signal subsequently passes through variable gain amplifiers 240. The antenna array 117 may receive signals from multiple remote terrestrial communication systems 120 simultaneously. The strength of the signals received by the antenna array 117 from two remote terrestrial communication systems 120 may vary significantly. Significant differences in signal strength may make numerical operations over the received signals infeasible or complicated for the reconfigurable digital logic processing device 114. The variable gain amplifiers 240 perform the function of signal levelling based on the commands or signals received from an automatic gain control loop 270. The automatic gain control loop 270 receives feedback from the reconfigurable digital logic processing device 114 regarding the strength of the received signals. The automatic gain control loop 270 working in combination with the variable gain amplifiers 240 maintains a suitable signal amplitude, despite variation of the signal amplitude of the IF1 signal.

In embodiments wherein the signals received by the antenna array 117 are dominated by noise, the RF front end 115 may be implemented with fixed gain (without variable gain amplifiers 240). In noise dominated received RF signals, the power level of transmissions by remote terrestrial communication system 120 may be similar to the power level of the noise component in the noise dominated received RF signal. Accordingly variable gain amplifiers 240 may not be necessary in processing noise dominated received RF signals as they may not meaningfully separate the noise component from the transmissions by remote terrestrial communication system 120. Similar signal levelling operations may be performed on signals transmitted by the LEO Satellite 110 in multiple directions of interest. Levelling of the signals transmitted by the LEO Satellite 110 in multiple directions of interest may be performed by the reconfigurable digital logic processing device 114 generating a signal provided to the RF front end 115 for transmission by the antenna array 117.

After the variable gain amplification, the signal IF1 passes through baluns 250. The baluns 250 convert the unbalanced signal UBIF1 to a balanced signal BIF1 suitable for downstream transmission and processing by the rest of the RF front end 115. The BIF1 signal is subsequently processed by an analogue to digital converter 255 to convert the analogue signals into a digital signal DIF2 suitable for processing by the reconfigurable digital logic processing device 114. The DIF2 signals may be 12-bit digital signals in some embodiments.

As illustrated in FIG. 2 , the reconfigurable digital logic processing device 114 (among other operations) channelizes the DIF2 signal into a plurality of spread spectrum modulated signals suitable for processing by spread spectrum receiver integrated circuits (ICs) 260. In some embodiments, the spread spectrum modulated signals may be signals encoded according to the LoRa™ protocol and the spread spectrum receiver integrated circuits 260 may be LoRa™ receiver ICs, such as Semtech™ SX1301 or SX1302 ICs, for example.

Blocks 222, 228, 232, 242 labelled “att.pad” in FIG. 2 are attenuation pads. In some embodiments, the attenuation pads may comprise three resistors arranged in a π configuration between the input and output points. The attenuation pads are configured to attenuate a signal by a fixed power level, for example 3 dB. The various attenuator pads in FIG. 2 allow adjustment of the power levels between the various signal processing stages to adjust the gain of a received signal to a desired overall gain level. The attenuator pads also attenuate signals rejected by one or more filters 230. For example, attenuation pad 228 may attenuate signals rejected by filter 230. By attenuating signals rejected by the one or more filters, the attenuator pads provide an improved impedance matching between the filters. The one or more filters of FIG. 2 may be reflective filters, i.e. the signals that do not pass through the filter get reflected. and could create stationary waves if a preceding component in the signal processing chain of FIG. 2 is not capable of absorbing the reflected signal. Such stationary waves could distort the frequency response of the various filters in FIG. 2 . The attenuation pads 222, 228 and 242 of FIG. 2 address the effects of the stationary waves by adjusting power levels between the various signal processing stages to adjust the gain of a received signal to a desired overall gain level.

The RF front end 115 may also process signals generated by the reconfigurable digital logic processing device 114 to enable transmission of the signals by the antenna array 117. The RF front end 115 may control a feeder signal provided to the antenna array 117 based on the signals provided by the reconfigurable digital logic processing device 114. Based on the feeder signal provided to the antenna array 117, the antenna array 117 may transmit signals in a pattern comprising one or more beams based on constructive and/or destructive interference of the radio frequency transmission. The directivity or direction of the one or more beams may be controlled by the signal provided by the reconfigurable digital logic processing device 114. The directivity or direction of the one or more beams may be controlled to correspond to the location of one or more remote terrestrial communication systems 120, thereby enhancing the quality of signals received by the remote terrestrial communication systems 120. In this way, multiple transmission beams can be simultaneously created and directed in multiple different terrestrial target directions.

In some embodiments, the LEO satellite 110 may comprise a separate reconfigurable digital logic processing device and a separate RF front end, both dedicated to transmission beamforming. In some embodiments, the reconfigurable digital logic processing device 114 and RF front end 115 may be configured to perform both transmission and reception beamforming. In some embodiments, there may be a common reconfigurable digital logic processing device 114 performing both transmission and reception beamforming and two separate RF front ends, one dedicated for transmission beamforming and another dedicated for reception beamforming.

FIG. 3 is a schematic diagram illustrating a part 300 of the reconfigurable digital logic processing device 114 according to some embodiments. At input points 301, 302, 303 and 304, a digital signal is received. Each input point corresponds to a signal received by a particular antenna element of the antenna array 117. This example corresponds to an exemplary antenna array with four elements. The signals received at input points 301 to 304 are the DIF2 signals described above with reference to FIG. 2 . The DIF2 signal is transmitted to a channelizer 310 to channelize the received signal into a number of separate channels. In some embodiments, the channelizer may separate the signal into 8 channelized signals, for example. The channelized signals are transmitted to multiple beamforming blocks 320. A separate beamforming block 320 is provided for each channel. Each beamforming block 320 processes the channelized signals received from each antenna element of the antenna array 117 to generate two beamformed signals for each channel. The number of beamformed signals in a channel depends on the number of antennas in the antenna array 117. By increasing the number of antennas in the antenna array, the number of beamformed signals for each channel may be increased to scale up the satellite communication service provided by the LEO satellite 110. In FIG. 3 , the beamformed signals are labelled 1A, 1B . . . NA, NB. Each beamformed signal corresponds to an independent channel of data modulated using a spread spectrum protocol, for example such as LoRa™.

The beamformed signals are then processed by a beam levelling block 330. Each beamformed signal is expected to have been received from a particular remote terrestrial communication system 120. Depending on the relative location of the remote terrestrial communication system 120 with respect to the LEO satellite 110, the signal received from the various remote terrestrial communication systems 120 may have different amplitude levels. The beam levelling blocks 330 perform the function of levelling the amplitude levels across the various beams corresponding to signals generated by different remote terrestrial communication systems 120. The beam levelling blocks 330 may perform beam levelling by dynamically adjusting a multiplication coefficient applied to the beamformed signals. Signal levelling through the beam levelling blocks 330 may be used alone or if necessary may be applied in combination with the signal levelling performed by the variable gain amplifiers 240 described with reference to FIG. 2 .

After beam levelling, the levelled beam signals are processed by beam base band down-conversion blocks 340. The beam base band down-conversion blocks 340 convert the levelled beamformed signals to a lower frequency signal at a lower sampling rate to meet the requirements of downstream signal processing components. The downstream signal processing components may include components that expect a spread spectrum modulated digital signal, for example a signal according to the LoRa™ protocol. In some embodiments, the beam base band down-conversion blocks 340 may generated a LoRa™ based signal 370 as output.

The reconfigurable digital logic processing device 114 also comprises diodes 305 and low pass filters 308 corresponding to each input point 301, 302, 303 and 304. In some embodiments, the low pass filters 308 pass signals with a frequency lower than 1 kHz or lower than 10 kHz, for example. The low pass filters 308 are configured to have a cut-off frequency significantly lower than the lowest frequency of the signals received or transmitted by the antenna array 117. In some embodiments, the low pass filters 308 may have a cut off frequency of around 5-6 kHz. The signals processed by the low pass filters 308 are added using a summing block 360 and a summed signal 365 is generated. The summed signal serves as an input to drive the automatic gain control loop 270 of FIG. 2 in embodiments that rely on the automatic gain control loop 270 for signal levelling.

FIG. 4 is a detailed block diagram of the beamforming block 320 of FIG. 3 . The beamforming block 320 receives phase and amplitude synchronous input signals in the IQ form from the channeliser 310 for each one of the antenna array elements 117 a to 117 n. A signal in an IQ form is a complex signal broken down into a real (in-phase) and imaginary (quadrature) components. The real component (I) corresponds to a cosine of the amplitude of a signal at a particular point in time (X axis component). The imaginary component (Q) corresponds to a sine of the amplitude of a signal at a particular point in time (Y axis component). In FIG. 4 , inputs 401, 403, 405, 407 correspond to the I component of the signals received from the respective antenna elements for a particular frequency channel as channelized by the channelizer 310. Inputs 402, 404, 406, 408 correspond to the Q component of the signals received from the respective antenna elements for the particular frequency channel corresponding to the inputs 401, 403, 405, 407 for the I component.

Processing blocks 470 and 475 define the mathematical operations that are performed on the signals received at inputs 401 and 402. The mathematical operations are performed by appropriately configuring the logical blocks and the interconnects of the reconfigurable logic processing device 114. For example, processing block 470 implements the operations in complex numbers:

I _(1A) =I _(Ant.1)(t).I _(Coef1A) −Q _(Ant.1)(t)Q _(Coef1A)

Q _(1A) =I _(Ant.1)(t).Q _(Coef1A) +Q _(Ant.1)(t).I _(Coef1A)

In the above mathematical operations, I_(Ant.1)(t) is a function corresponding to I component of the signal received by antennal element Ant.1 that corresponds to the input at 401. Similarly Q_(Ant.1)(t) is a function corresponding to Q component of the signal received by antennal element Ant.1 that corresponds to the input at 402. I_(Coef1A) and Q_(Coef1A) are coefficients that control the result of the mathematical operation on the received signals. Processing block 470 performs similar operations of the signals 401 and 402 using the coefficients I_(Coef1B) and Q_(Coef1B). The rest of the processing blocks within the beamforming block 320 perform similar operations to the rest of the signals received at inputs 403 to 408 using a distinct set of coefficients stored in memory 113. These coefficients may also be described as weights corresponding to each antenna element.

Each antenna element has at least 4 coefficients or weights labelled I_(Coef1A), Q_(Coef1A), I_(Coef1B) and Q_(Coef1B) These coefficients or weight are dynamic and are varied by the beamforming block 320 on instructions from the processor 112. The processor 112 varies these coefficients based on the orbital schedule data 118 and information regarding a current position of the LEO satellite 110. In some embodiments, the LEO satellite 110 may receive command instructions from ground station 130 over the communication link 170. The command instructions may comprise instructions to the processor 112 to vary the coefficients depending on a change in the needs from the communication system 100. The change in communication needs may include the addition or removal of particular remote terrestrial communication systems 120 to the communication schedule. The change in the communication needs may also include identification of a source of interference or noise along certain parts of the LEO path and implementing beam nulling at appropriate times or time periods along the LEO path to address the source of interference or noise.

The orbital schedule data 118 includes antenna array configuration records. Each antenna array configuration record comprises an ephemeris record or an ephemeris zone record and weights or coefficients associated with each antenna array element in relation to the ephemeris record. The ephemeris record defines a zone or part of the orbit of the LEO satellite 110. Given a current position of the LEO satellite 110, the processor 112 is able to determine which ephemeris record the current position of the satellite corresponds to. After determining the ephemeris record that the current position of the satellite corresponds to, the processor 112 retrieves the weights or coefficients associated with each antenna array element in relation to the ephemeris record. The processor 112 subsequently reconfigures the coefficients of the beamforming block 320 based on the retrieved weights. Once the weights or coefficients of the beamforming block 320 are reconfigured, the reconfigurable digital logic processing device 114 processes the signals received by the antenna array 117 to best amplify the signals transmitted by the one or more remote terrestrial communication systems 120 that are part of the communication system 100 and currently fall within the field of view of the antenna array 117 of the LEO satellite 110.

Processing block 470 processes the input signals 401 and 402 to generate output signals 409 and 410. The output signals produced by the various mathematical operations illustrated in FIG. 4 are added by the summation block 460 to produce intermediate signals 411 and 412. If the processing by block 470 is performed using 12 bit integers as input signals, for example, the output may be a 24 bit integer signal in order to not lose any information in the determination of intermediate signals 411 and 412. The intermediate signals 411 and 412 are divided by the division blocks 480 to obtain output signals 413 (I component) and 414 (Q component) that together are described as beam 1A. Each division block 480 transforms a 24 bit input signal into a 12 bit output signal. Beamforming block 320 also generates an output signal described as beam 1B. Each of the beams 1A and 1B comprise an I and Q component. Each beam may correspond to signals transmitted by (and received from) a specific remote terrestrial communication system 120. In some embodiments, the processing block 470 may be configured to perform fixed point operations whereby the number of bits generated from the multiplication operations with the I and Q components of the weight may be fixed. In such embodiments, the block 480 may not be necessary for reducing the number of bits in the output signal.

The reconfigurable digital logic processing device 114 may similarly comprise transmission beamforming blocks that generate a signal provided to the RF front end 115 based on transmission beamforming coefficients or weights stored in the memory 113 to enable transmission beamforming using the antenna array 117.

FIG. 5 is a circuit diagram of a RF front end 500 according to some embodiments. The RF front end 500 can be substituted for the RF front end 115 in some embodiments. The RF front end 500 comprises a series of amplifiers, band pass filters and two variable gain amplifiers to condition the signals received by the antenna array 117 to be suitable for processing by the reconfigurable digital logic processing device 114. Each antenna element 117 a through 117 n may correspond to antenna element 530. In some embodiments, to handle noise-dominated received signals, the variable gain amplifiers may be replaced by fixed gain amplifiers.

The RF front end 500 comprises a series of band pass filters 501, 504, 507, 517 and 522. In some embodiments, the band pass filters 501, 504 and 507 may pass signals with a frequency from 1980 MHz to 2010 Mhz with a loss of 0.7 dB, for example. In some embodiments, the band pass filters 501, 504 and 507 may be implemented using a muRata SF2234E-1 filter, for example. In some embodiments, the band pass filters 517 and 522 may pass signals with a frequency from 938 MHz to 902 Mhz with a loss of 3 dB. In some embodiments, the band pass filters 517 and 522 may be implemented using a muRata SF2098H filter, for example.

The RF front end 500 comprises a series of amplifiers 502, 505, 508, 510, 515, 520 and 526. In some embodiments, amplifiers 502, 505, 508 and 510 may have a gain of 20 dB, a noise figure of 0.7 dB, an output intercept point (OIP3) of 17.5 dBm, for example. In some embodiments, amplifiers 515 and 520 may have a gain of 23 dB, a noise figure of 0.7 dB, an output intercept point (OIP3) of 17.5 dBm, for example. In some embodiments, amplifier 526 may have a gain of 22 dB, a noise figure of 1.5 dB, an output intercept point (OIP3) of 28 dBm, and an OP1 dB gain compression parameter value of 18 dBm, for example. In some embodiments, amplifiers 502, 505, 508, 510, 515 and 526 may operate at 3V, using a 6 mA current and drain 20 mW of power, for example.

The RF front end 500 comprises variable gain amplifiers 518 and 523. The variable gain amplifiers 518 and 523 may have a variable gain value from −23 dB to 17 dB, a noise figure of 5 dB (including attenuator insertion loss), and an OIP3 value of 34 dBm, for example. The variable gain amplifiers 518 and 523 may operate on 5V, using 110 mA current and drain 550 mW power, for example. In some embodiments, the variable gain amplifiers 518 and 523 may be implemented using a Maxim Integrated MAX2092 variable gain amplifier, for example.

The RF front end 500 comprises attenuator pads 503, 506, 509, 511, 516, 519, 521 and 524. In some embodiments, the attenuator pads 503, 506, 509, 511, 516, 519, 521 and 524 may each have a loss value of 3 dB, for example. The RF front end 500 comprises baluns 512, 514 and 527. The RF front end 500 comprises a frequency mixer 513. In some embodiments, the frequency mixer 513 has a gain of 1 dB, a noise factor of 12 dB and OIP3 of 22 dBm, for example. In some embodiments, the frequency mixer 513 may operate at 3.3V, using 95 mA current and drain 320 mW power, for example. The RF front end 500 comprises an analog to digital signal converter 528. In some embodiments, the analog to digital signal converter 528 may operate at a power level of 4 dBm, for example.

FIG. 6 is a graph 600 illustrating an array factor for an exemplary 4 element antenna array 117 with the below antenna array weights or coefficients:

TABLE 1 Line Amplitude Length I-Q Coefficients for DBF I Q (dB) (mm) Antenna 1 Coefficients 1151 0 −5.00 0.00 Antenna 2 Coefficients 2047 0 0.00 0.00 Antenna 3 Coefficients 2047 0 0.00 0.00 Antenna 4 Coefficients 1151 0 −5.00 0.00

The reconfigurable digital logic processing device 114, when incorporating the coefficients of table 1, processes the signals received by the antenna array according to a transfer function graphically represented by the graph 600 of FIG. 6 . The antenna array coefficients effectively define the transfer function. The x axis of graph 600 corresponds to the inclination (i.e. receive direction) of the arriving radio waves and the y axis corresponds to the amplification level. At point 610 that corresponds to 0 degrees, the amplification level is maximum (0). At point 620 that corresponds to about 40 degrees, the amplification level is minimum. With the array factor of graph 600, any signals received at about 40 degrees are significantly attenuated or nullified. In this configuration, the 0 degree direction may be configured to correspond to an expected location of a remote terrestrial communication system 120 at a particular period of the LEO satellite orbit as defined by the orbital schedule data 118. The 40 degree direction may correspond to a known source of interference producing a signal not of interest to the communication system. Line length values in table 1 indicate the electrical connection length between the corresponding element of the antenna array 117 and the RF Front end 115. Electrical length is the length as seen by the electrical signals, which propagate slower in a medium with higher relative permittivity or permeability. In some embodiments, different antenna array elements may have different line length values. Differences in line length may be corrected or accommodated by changes in the I, Q coefficient.

FIG. 7 is a graph 700 illustrating an array factor for an exemplary 4 element antenna array 117 with the below antenna array weights or coefficients:

TABLE 2 Line Amplitude Length I-Q Coefficients I Q (dB) (mm) Antenna 1 Coefficients 861 −1856 0.00 0.00 Antenna 2 Coefficients 1901 −757 0.00 0.00 Antenna 3 Coefficients 1901 758 0.00 0.00 Antenna 4 Coefficients 861 1857 0.00 0.00

The reconfigurable digital logic processing device 114 when incorporating the coefficients of table 2 processes the signals received by the antenna array according to the array factor in graph 700 of FIG. 7 . The antenna array coefficients of Table 2 effectively define the transfer function that is graphically represented by graph 700. At point 710 that corresponds to 15 degrees on the x axis, the amplification level is maximum (0). At points 720, 730, 740 that correspond to about −15, 50 and −55 degrees respectively, the amplification level is minimum. With the array factor of graph 700, any signals received at about −15, 50, −55 degrees are significantly attenuated or nullified. In this configuration, the 15 degree direction may correspond to a remote terrestrial communication system 120. The −15, 50, −55 degree directions may correspond to a source of interference producing a signal not of interest to the communication system. The array factor in graph 700 comprises three sidelobes 712, 714 and 716 corresponding to separate ranges of beam angles. Since the antenna array 117 as configured according to antenna array configuration parameters of table 2 has uniform excitation levels, the sidelobes 712, 714 and 716 are only around 12 dB lower in peak gain levels when compared to the main lobe 710. In embodiments where several beams are required on a common frequency channel, it may be necessary to have sidelobes with a more significantly lower gain level. FIG. 8 provides an example of a configuration of the antenna array where the sidelobes have a more significantly lower gain level.

FIG. 8 is a graph 800 illustrating an array factor for an exemplary 4 element antenna array 117 with the below antenna array weights or coefficients:

TABLE 3 Line Amplitude Length I-Q Coefficients I Q (dB) (mm) Antenna 1 Coefficients 484 −1044 −5.00 0.00 Antenna 2 Coefficients 1901 −757 0.00 0.00 Antenna 3 Coefficients 1901 758 0.00 0.00 Antenna 4 Coefficients 484 1045 −5.00 0.00

The reconfigurable digital logic processing device 114 when incorporating the coefficients of table 3 processes the signals received by the antenna array according to the array factor in graph 800 of FIG. 8 . The antenna array coefficients of Table 3 effectively define the transfer function that is graphically represented by graph 800. At point 810 that corresponds to 15 degrees on the x axis, the amplification level is maximum (0). At points 820, 830, 840 that correspond to about −15, 50 and −55 degrees respectively, the amplification level is minimum. With the array factor of graph 800, any signals received at about −15, 50, −55 degrees are significantly attenuated or nullified. In this configuration, the 15 degree direction may correspond to a remote terrestrial communication system 120 that the LEO satellite 110 is scheduled to communicate with along a particular part of the satellite path. The −15, 50, −55 degree directions may correspond to sources of interference producing a signal not of interest to the communication system along the same part of the satellite path. Configuration of the antenna array 117 based on the configuration parameters of table 3 results in a tapered excitation of the antenna array, wherein the edge (antenna array) elements 1 and 2 are excited at −5 dB. Because of the tapered excitation based on the configuration parameters of table 3, the peaks of the sidelobes (corresponding to angle ranges 812, 814) are more than 20 dB lower (on the y axis) than the peak (810) of the array factor 800. The significant difference in the levels of gain between the main lobe and the various sidelobes may be advantageous in embodiments where several beams are required for a common frequency channel. The configuration of the antenna array 117 using parameters similar to the parameters exemplified in table 3 may provide improved independence between multiple steered beams sharing a common channel frequency, while improving the overall communication bandwidth and parallelism of the satellite communication system 100.

FIG. 9 is a graph 900 illustrating an array factor for an exemplary 4 element antenna array 117 with the below antenna array weights or coefficients:

TABLE 4 Line Amplitude Length I-Q Coefficients I Q (dB) (mm) Antenna 1 Coefficients 2047 0 0.00 0.00 Antenna 2 Coefficients 2047 0 0.00 0.00 Antenna 3 Coefficients 2047 0 0.00 0.00 Antenna 4 Coefficients 2047 0 0.00 0.00

The reconfigurable digital logic processing device 114 when incorporating the coefficients of table 4 processes the signals received by the antenna array according to the array factor in graph 900 of FIG. 9 . The antenna array coefficients of Table 4 effectively define the transfer function that is graphically represented by graph 900. At point 910 that corresponds to 0 degrees on the x axis, the amplification level is maximum (0). At points 920 and 930 that correspond to about −30 and −30 degrees respectively, the amplification level is minimum. With the array factor of graph 900, any signals received at about −30 and 30 degrees are significantly attenuated or nullified. In this configuration, the 0 degree direction may correspond to a remote terrestrial communication system 120. The −30 and 30 degree directions may correspond to a sources of interference producing a signal not of interest to the communication system.

The array factor graph 900 of FIG. 9 may be contrasted with the array factor graph 600 of FIG. 6 . The array factor graph 600 is generated using a 5 dB taper on antenna 1 and antenna 2 (edge elements of the antenna array). In contrast, the array factor graph 900 is generated using uniform excitation. This difference in the excitation in the configuration for the array factor graph 600 and 900 results in generating sidelobes (corresponding to angle ranges 612, 614) in the array factor graph 600 that are significantly lower than the sidelobes (corresponding to angle ranges 912, 914) in the array factor graph 900. Further, because of the differences in the configuration parameters that result in the array factor graphs 600 and 900, the main beam (corresponding to angle range 910) of the array factor graph 900 is slightly narrower than the main beam (corresponding to angle range 610) of array factor graph 600. Accordingly, as illustrated by FIGS. 6 to 9 , by modifying antenna array weights or coefficients, different configurations of antenna array factors (and thereby transfer functions) may be obtained to meet changing communication requirements of the satellite communication system 100.

FIG. 10 is a graph 1000 illustrating an array factor for an exemplary 4 element antenna array 117 with the below antenna array weights or coefficients:

TABLE 5 Line Amplitude Length I-Q Coefficients I Q (dB) (mm) Antenna 1 Coefficients −2047 0 0.00 0.00 Antenna 2 Coefficients −2047 0 0.00 0.00 Antenna 3 Coefficients 2047 0 0.00 0.00 Antenna 4 Coefficients 2047 0 0.00 0.00

The reconfigurable digital logic processing device 114 when incorporating the coefficients of table 5 processes the signals received by the antenna array according to the array factor in graph 1000 of FIG. 10 . The antenna array coefficients of Table 5 effectively define the transfer function that is graphically represented by graph 1000. At point 1030 that corresponds to 0 degrees on the x axis, the amplification level is minimum (and the attenuation level is maximum). At points 1020 and 1010 that correspond to about −25 and 25 degrees respectively, the amplification level is maximum (and the attenuation level is minimum). With the array factor of graph 1000, any signals received at 0 degrees inclination are significantly attenuated or nullified. In this configuration, the −25 and 25 degree directions may correspond to remote terrestrial communication systems 120, for example. The 0 degree direction may correspond to a source of interference producing a signal not of interest to the communication system, for example.

FIG. 11 is a schematic diagram of an antenna array 1100 comprising antenna elements 1100 a, 1100 b, 1100 c and 1100 d according to some embodiments. The antenna array 1100 is a phased antenna array. FIG. 11 also illustrates the Z and Y axis used as a reference for the calculations performed by the reconfigurable digital logic processing device 114 and the RF front end 115. The X axis (not shown) is perpendicular to the Y and Z axis. Other orientations of the X, Y and Z axes may be used in other embodiments.

In some embodiments, the antenna array 117 or 1100 may be a patch antenna array suitable for positioning or mounting on a flat surface. Each element of the antenna array may be a patch of metal mounted on a larger sheet of metal 1190 serving as a ground plane for the antenna array. In other embodiments, the antenna array 117 or 1100 may include multiple ones of other forms of radiating element, such as a whip radiating element or a horn radiating element, for example. However, the antenna elements of the antenna array 117 or 1100 are not configured to move relative to each other, nor does the antenna array rely on a diversity setup.

FIG. 12 is an example plan view of an antenna array 117 or 1100 in the form of a patch antenna array 1200 of the communication system according to some embodiments. The patch antenna array 1200 is shown as a linear array. Antenna elements of a linear array are positioned along one linear dimension, i.e. the antenna elements are positioned along one line to form the patch antenna array. The patch antenna array 1200 is shown as an array of antenna elements situated on a common base plane defined by the chassis. Each antenna element or patch 1200 a, 1200 b, 1200 c, 1200 d of the patch antenna array 1200 has a cupped stacked patch configuration. In some embodiments, the spacing between adjacent antenna element or patch 1200 a, 1200 b, 1200 c, 1200 d remains substantially uniform. The antenna array 1200 also comprises two coaxial probes 1210 and 1220. The probes 1210 and 1220 are orthogonal to each other (i.e. angularly separated by about 90 degrees relative to a centre post 1440) and may be axially fixed to withstand vibrations during a launch of the LEO satellite 110. In some embodiments, the antenna array 1200 may have the dimensions of 81 mm×301 mm×15 mm, for example. In some embodiments, the antenna array 117 may alternatively be implemented using a rectangular array, multiple linear arrays or a circular or other non-linear array, for example. A uniform or non-uniform distance may be used to space the antenna elements of the rectangular array or the circular array.

FIG. 13 is a plan view of an example antenna array element 1200 a of the antenna array 1200 according to some embodiments. The probes 1220 and 1210 make contact with the antenna array element 1200 a at points Y and X respectively.

FIG. 14 is a further plan view of an example antenna array element 1200 a of the antenna array 1200 according to some embodiments. FIG. 14 illustrates a first (upper) strip/patch 1410, a second (lower) strip/patch 1420 and a cup 1430. Each cup 1430 is embedded in or positioned on or incorporated in an outer part or subframe of a chassis of the LEO satellite 110, for example. The patches 1410 and 1420 may be embossed with a thinner patch for greater mechanical stability. The two patches 1410 and 1420 are mechanically supported by a centre post 1440. The lower patch 1420 is galvanically excited via the two orthogonal coaxial probes 1220 and 1210. In some embodiments, underneath patch 1420 lies a microstrip hybrid network (not shown).

The microstrip hybrid network may create two ports, one Right Hand Circular Polarised (RHCP) port and another Left Hand Circular Polarised (LHCP) port. Accordingly, some embodiments use left hand or right hand circular polarisation of transmissions. Incorporation of left hand or right hand circular polarisation of transmissions allows for a simultaneous transmission of two independent signals, a first signal using the RHCP port and a second signal using the LHCP port. The two simultaneously transmitted signals comprise oscillations in planes orthogonal to each other, as opposed to oscillation in a singularly polarised transmission. Circularly polarised transmissions are more robust in response to problems associated with signal reflection or lack of a clear line of sight to a transmission target.

FIG. 15 is a side cross section view of the antenna array element 1200 a shown in FIG. 14 . The cup 1430 has an opening 1510 through which both the probes 1210, 1220 pass towards the patches 1410 and 1420.

FIG. 16 is a close-up cross-sectional side view of a probe part 1600 of the antenna array element 1200 a of the antenna array 1200 according to some embodiments. The probe part 1600 comprises coaxial probes 1630 and 1650. In some embodiments, the coaxial probes 1630 and 1650 may have an impedance of 50 ohms. The probes are surrounded by a Teflon sleeve 1610 which is in turn surrounded by an aluminium ground base 1660. At the bottom of the probe part is a ground plane 1640. Between ground plane 1640 and a surface of a chassis of the LEO satellite 110 lies a microstrip 1620. In some embodiments, the microstrip 1620 may have an impedance of 50 ohms. At the bottom of the coaxial probe 1630 lies a conductor, such as a whisker copper wire 1670, according to some embodiments. The whisker copper wire 1670 connects the probes 1630 and 1650 to the microstrip 1620. In some embodiments, the whisker copper wire 1670 may be soldered using a Sn96/Ag4 alloy solder. A dielectric supporting the microstrip 1620 may be Rodgers RT-Duroid 6002 (Relative Permittivity 2.94) with dielectric thickness 508 μm (about 0.5 mm), and metallization on both sides at 17 μm (0.017 mm) of Copper thickness, for example.

FIG. 17 is a top view of a ground plane 1700 of the antenna array element 1200 a, according to some embodiments. The ground plane 1700 defines an etched area or a discontinuous area 1710 such that the Teflon sleeve 1610 does not contact the ground plane 1700.

The phased antenna array of various embodiments disclosed herein is advantageously suited to the creation of multiple simultaneous transmit or receive beams (or to beam nullification) in multiple directions. This increases the communication efficiency of the LEO satellite 110.

In embodiments related to a 6U CubeSat, spatial limitations on the 6U selected satellite chassis platform resulted in the need to fit the antenna array into a maximum of 310×90×14 mm³ volume on one side of the satellite body.

In order to perform array beam scanning, the radiating elements in the array should not be arbitrarily separated, but should have a separation distance as a function of the array beam scan angular range. If the antenna element to antenna element spacing is too large, grating lobes (which are a sort of parasitic radiation lobe) can appear in the antenna radiation patterns. Such grating lobes can be detrimental to the performance of the antenna system by reducing signal transmission efficiency which can ultimately negatively affect the performance of the whole satellite.

In some embodiments based on a 6U chassis, a 75 mm (centre to centre) antenna element to antenna element separation may be used for communication in S-band frequencies. The adjacent edges of adjacent antenna elements may be separated by about 3 mm to about 5 mm, for example. Antenna accommodation on the satellite can be more of a performance limiting factor than the RF performance (i.e. avoiding grating lobes) in some embodiments. The desired RF performance of the antenna array can be maintained in receive mode with an antenna element to antenna element spacing of 78 mm without significant changes, if the spatial accommodation of the antenna array on the satellite allows for such antenna element to antenna element spacing.

As a general rule, the performance of a patch antenna is reduced in terms of bandwidth when the element is small, and/or extremely low profile. To achieve the RF performance desired for satellite communication functionality of 6U satellite embodiments as described herein but with an element that could fit into an array cell with a maximum length of 75 mm, lengthwise compression or surface variation of patch radiators of the antenna elements may be employed.

A wave or corrugation may be formed in the surface and cross sectional profile of the patch radiators to increase their RF electrical lengths while maintaining the reduced mechanical length. The waving or corrugation of the patch surface allows a physical patch size reduction of a few percent, but this may be sufficient to allow the desired RF performance within the constrained physical space of the CubeSat chassis.

However, the wave or corrugation patterning of the patch surface may introduce manufacturing challenges as it is not suitable for conventional machining of patch antenna radiators. According to some embodiments, 3D printing of the patch antenna in Aluminium with the wave or corrugation patterning can be used for the manufacturing of the patch antenna. However, 3D printing of the wavy or corrugated patches is challenging because of the shape and nature of the patch antenna and the physical constraints of 3D printing machines.

FIG. 18 is a perspective view of a chassis 1800 of an LEO satellite according to some embodiments. The chassis 1800 has an example size of 6 CubeSat units (i.e. 6U). The chassis 1800 has an orientation wherein 3 CubeSat units are positioned lengthwise adjacent to 3 CubeSat units to provide the 6 CubeSat unit overall size. Various components of the LEO Satellite 110 may be positioned within or on the chassis 1800. The chassis 1800 is normally covered by covering plates and/or materials and when so covered comprises a first major face 1810 (corresponding to an area of 6 units) and a second major face (corresponding to an area of 6 units, not shown) opposite the first major face 1810. The chassis 1800, when covered by covering plates and/or materials, comprises a first minor face 1820 (corresponding to an area of 3 units) and a second minor face (corresponding to an area of 6 units, not shown) opposite the first minor face 1820. The chassis 1800, when covered by covering plates and/or materials, comprises a first side face 1830 and a second side face (not shown) opposite the first side face 1830.

In some embodiments, the antenna array 117 or 1100 is positioned on the first minor face 1820, leaving the first major face 1810 and the second major face available for positioning of solar cells. Alternatively, or in addition, the antenna array 117 or 1100 may be disposed on the second minor face. The antenna array 117 or 1100 may extend across multiple CubeSat units, for example, and may extend across substantially the whole length of the first minor face 1820 and/or the second minor face.

Since the first and second major faces have the greatest surface area, positioning the antenna array 117 or 1100 on the first minor face 1820 and/or the second minor face allows for larger generation of solar power for use within the LEO satellite. In some embodiments, the antenna array 117 or 1100 may be positioned on the first and/or second major face to accommodate an antenna array larger in an area than the first minor face 1820 and/or second minor face. In some embodiments, the antenna array 117 or 1100 may include array portions disposed on the first side face 1830 and/or second side face. The at least one processor 112 is configured to control orientation mechanisms of the LEO satellite 110 to consistently adopt an orientation that points the antenna array 117 or 1100 toward the centre of the earth.

FIG. 19 is a schematic view of an LEO Satellite 1900 according to some embodiments. The LEO satellite 1900 incorporates the chassis 1800 to form a body of the LEO satellite 1900. The LEO satellite 1900 comprises solar cells 1910 on part of the first major face 1810 and antenna array 117 or 1100 on part of the first minor face 1820.

FIG. 20 is a flowchart of a method 2000 of communication between the LEO satellite 110 and the plurality of terrestrial communication system 120. Various steps of method 2000 are performed by the various components of the LEO satellite 110 including the antenna array 117, reconfigurable digital logic device 114 and processor 112. At 2010, a current position of the LEO satellite is determined. In some embodiments, the current position may be determined using data from the GPS receiver. In some embodiments, a current position of the LEO satellite may be determined using an initial satellite state vector comprising position and velocity data provided by the satellite launch provider at the point of time the LEO satellite 110 was launched from a launch vehicle.

At 2012, the processor 112 determines array factor coefficients based on the satellite position determined at 2010. The array factor coefficients may be retrieved from memory 113 storing orbital schedule data 118. The array factor coefficients may be suitable for allowing transmission or reception beamforming operations.

At 2014, the processor 112 reconfigures the reconfigurable digital logic processing device 114 using the array factor coefficients determined at 2012. The schematic diagram of FIG. 4 illustrates signal processing operations performed by a digital logic processing device 114 of some embodiments. At step 2014, the various coefficients illustrated in FIG. 4 may be updated based on the array factor coefficients determined at 2012. The table below illustrates an example of the records stored in memory 113 that may be used to configure reconfigurable digital logic processing device 114, in particular to configure the I and Q array factor coefficients that determine the beamforming or beam steering operations performed by the LEO satellite 110.

TABLE 6 Flight Path Coordinates I, Q coefficient of LEO Satellite values for each (latitude, longitude) antenna element Comments (−26.298283646981687, Antenna 1 [−872, 540] This example corresponds to the 103.49188047624469) to Antenna 2 [−223, −2035] LEO satellite being positioned (−15.225829293439313, Antenna 3 [1933, 674] westward off the western coast of 117.37859865239922) Antenna 4 [−722, 729] Australia. The coefficients allow the beams to be directed eastwards with respect to the satellite to cover remote terrestrial communication systems positioned in Western Australia. (−34.48717708853079, Antenna 1 [−1003, 214] This example corresponds to the 14.09200067105491) to Antenna 2 [1767, 1033] LEO satellite being positioned (−34.97309413652626, Antenna 3 [−610, −1954] south off the southern coast of 30.203706711591614) Antenna 4 [−434, 930] South Africa. The coefficients allow the beams to be directed northwards with respect to the satellite to cover remote terrestrial communication systems positioned in South Africa.

The orbital schedule data 118 of the LEO satellite 110 may comprise the flight path coordinates as exemplified in table 6 above. Ephemeris records stored in memory 118 indicating a scheduled position or a portion of a flight path of the LEO satellite 110 may also include the flight path coordinates as exemplified in table 6 above.

At 2016, the antenna array 117 may receive signals. The received signals are processed by the RF front end 115 and made available to the digital logic processing device 114. At 2018, the digital logic processing device 114 processes the signals received by the antenna array 115 to amplify a subset of received signals corresponding to terrestrial communication system 120. At 2018, the digital logic processing device 114 may also simultaneously attenuate signals that are not of interest or signals corresponding to known sources of noise. At 2020, the amplified subset of signals determined at 2018 are processed to determine information encoded in the signals received at 2016 by the antenna array 117. Step 2020 may be performed in its entirety by the digital logic processing device 114 or the processor 112. In some embodiments, step 2020 may be performed by the digital logic processing device 114 and the processor 112 in coordination with each other. The decoded information may be stored in memory 113. When the LEO satellite 110 establishes communication with ground station 130, the decoded information may be transmitted to the ground station 130 over the radio communication link 170 to be made available to client device 140.

Steps 2022, 2024 and 2026 correspond to steps for transmission of information from the LEO satellite 110 to a remote terrestrial communication system 120. At 2022, the processor 112 retrieves the information/payload to be transmitted from memory 113. The retrieved information/payload is made available to the reconfigurable digital logic processing device 114. At 2024, the reconfigurable digital logic processing device 114 processes the information/payload to generate a feed signal for the antenna array 117. The generated feed signal is determined based on the array factor coefficients used to dynamically reconfigure the digital logic processing device 114 to allow transmission beam forming in a desired direction of interest for transmission corresponding to the remote terrestrial communication system 120 or ground station 130. The feed signal is made available to the antenna array 117 through the RF front end 115. At step 2026, the antenna array 117 transmits the signal based on the feed signal generated by the reconfigurable digital logic processing device 114.

The method 2000 as performed by the various components of the LEO satellite 110 may be continuously or repeatedly performed at regular intervals. After completion of step 2020 or after completion of the step 2026, the method 2000 may continue at step 2010 by determining a change in the position of the satellite followed by the rest of the steps of the method 2000 as described.

FIG. 21 is a flowchart of a method 2100 of launching a satellite launch vehicle configured to deploy in orbit the LEO satellite 110. At step 2102 an LEO satellite 110 according the embodiments is provided to a satellite launch vehicle. The LEO satellite 110 may be integrated in a dispenser system which provides an interface between the LEO satellite and the launch vehicle, protects the LEO satellite 110 during flight and allows the deployment of the LEO satellite as commanded by the launch vehicle. At step 2104, the satellite launch vehicle configured to release the LEO satellite 110 is launched from the surface of the earth, following which the LEO satellite can be deployed for travel in a particular orbit.

Some embodiments relate to installation in and/or on a microsatellite or nanosatellite chassis or housing: at least one processor, a memory accessible to the at least one processor, the memory storing an orbital schedule of a LEO satellite, and a communication sub-system accessible to the at least one processor. The communication sub-system comprises: an antenna array comprising two or more antenna elements; and a reconfigurable digital logic processing device in communication with the antenna array. The at least one processor is in communication with the reconfigurable digital logic processing device, and the at least one processor is configured to dynamically reconfigure the reconfigurable digital logic processing device to perform directional beamforming based on the orbital schedule by applying different transfer functions to signals simultaneously received or transmitted by multiple antenna elements of the antenna array over time. The installation of the communication subsystem and other components as described may form an early part of the step 2102 of providing described above.

Some embodiments relate to a method for providing a satellite communication service, comprising providing a LEO satellite of any one of the embodiments as a payload to a satellite launch vehicle.

Some embodiments relate to a method for providing a satellite communication service, comprising launching the satellite launch vehicle configured to release the LEO satellite of any one of the embodiments for travel in a low earth orbit.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. 

1. A low earth orbit (LEO) satellite, the LEO satellite comprising: a microsatellite or nanosatellite chassis housing at least one processor, a memory accessible to the at least one processor, the memory storing an orbital schedule of the LEO satellite, and a communication sub-system accessible to the at least one processor; the communication sub-system comprising: an antenna array comprising two or more antenna elements; a reconfigurable digital logic processing device in communication with the antenna array; wherein the at least one processor is in communication with the reconfigurable digital logic processing device, and wherein the at least one processor is configured to dynamically reconfigure the reconfigurable digital logic processing device to perform directional beamforming based on the orbital schedule by applying different transfer functions to signals simultaneously received or transmitted by multiple antenna elements of the antenna array over time.
 2. The LEO satellite of claim 1, wherein the antenna array is a linear array.
 3. The LEO satellite of claim 1, wherein the directional beamforming is performed using all antenna elements of the antenna array simultaneously.
 4. The LEO satellite of claim 1, wherein the at least one processor is further configured to dynamically reconfigure the reconfigurable digital logic processing device to perform directional beam-nulling based on the orbital schedule by applying different transfer functions to signals received and transmitted by multiple antenna elements of the antenna array over time.
 5. The LEO satellite of claim 4, wherein the directional beamforming and/or beam-nulling is performed simultaneously across multiple frequency channels.
 6. The LEO satellite of claim 4, wherein the directional beamforming and/or beam-nulling is performed simultaneously in multiple different directions.
 7. The LEO satellite of claim 1, wherein the antenna array is disposed along one side of the chassis.
 8. The LEO satellite of claim 1, wherein the antenna array is disposed to substantially cover a minor face of the chassis.
 9. The LEO satellite of claim 1, wherein each of the antenna elements includes a patch antenna.
 10. The LEO satellite of claim 1, wherein the antenna array includes at least four antenna elements.
 11. A low earth orbit (LEO) satellite, the LEO satellite comprising: a chassis housing at least one processor, a memory accessible to the at least one processor, the memory storing an orbital schedule of the LEO satellite, and a communication sub-system accessible to the at least one processor; the communication sub-system comprising: an antenna array comprising two or more antenna elements; a reconfigurable digital logic processing device in communication with the antenna array; wherein the at least one processor is in communication with the reconfigurable digital logic processing device, and wherein the at least one processor is configured to dynamically reconfigure the reconfigurable digital logic processing device to: process signals received by the antenna array to amplify transmissions received from one or more directions of interest according to an orbital schedule of the LEO satellite, or amplify signals to be transmitted by the antenna array in one or more directions of interest for transmission according to the orbital schedule of the LEO satellite; and the LEO satellite has a mass in the range of 1 kg to 100 kg.
 12. The LEO satellite of claim 1, wherein the LEO satellite has a mass in the range of 10 kg to 50 kg.
 13. The LEO satellite of claim 1, wherein the chassis has a CubeSat structure and a size from 1 CubeSat unit to 50 CubeSat units.
 14. The LEO satellite of claim 12, wherein the chassis has a CubeSat structure and a size from 3 CubeSat units to 24 CubeSat units.
 15. The LEO satellite of claim 1, wherein the chassis comprises a major face, a minor face, the major face having a greater surface area than the minor face; and the antenna array is provided on at least a part of the minor face.
 16. The LEO satellite of claim 1, wherein the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to: process the signals received by the antenna array to attenuate transmissions received from one or more directions not of interest according to the orbital schedule of the LEO satellite, or attenuate signals to be transmitted by the antenna array in one or more directions not of interest for transmission according to the orbital schedule of the LEO satellite.
 17. The LEO satellite of claim 1, wherein the orbital schedule data comprises one or more antenna array configuration records, each antenna array configuration record comprising: an ephemeris record indicating a scheduled position of the LEO satellite in orbit over a period of time; and array factor coefficients associated with each of the two or more antenna elements defined in relation to the ephemeris record.
 18. The LEO satellite of claim 17, wherein each array factor coefficient is a complex number weight comprising a real coefficient value and an imaginary coefficient value.
 19. The LEO satellite of claim 17, wherein the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to process the signals received by the antenna array or amplify signals transmitted by the antenna array based on the scheduled position of the LEO satellite and the array factor coefficients as defined in the antenna array configuration record associated with the scheduled position of the LEO satellite.
 20. The LEO satellite of claim 11, wherein the antenna array is a patch antenna array.
 21. The LEO satellite of claim 1, further comprising an analog to digital converter for pre-processing signals before processing by the reconfigurable digital logic processing device.
 22. The LEO satellite of claim 1, further comprising a digital to analog converter for processing signals generated by the reconfigurable digital logic processing device for transmission by the antenna array.
 23. The LEO satellite of claim 1, further comprising a signal channeliser for channelising signals before processing by the reconfigurable digital logic processing device.
 24. The LEO satellite of claim 1, wherein the reconfigurable digital logic processing device comprises a Field Programmable Gate Array (FPGA).
 25. The LEO satellite of claim 1, wherein when the LEO satellite receives signals from more than one directions of interest, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to level amplitudes of signals received from the more than one directions of interest.
 26. The LEO satellite of claim 1, wherein when the LEO satellite transmits signals to multiple directions of interest, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to level amplitudes of signals transmitted to the multiple directions of interest.
 27. The LEO satellite of claim 1, further comprising one or more variable gain amplifiers (VGAs) in communication with the at least one processor, wherein when the LEO satellite receives signals from more than one directions of interest, the at least one processor configures the one or more VGAs to level amplitudes of signals received from the more than one directions of interest.
 28. The LEO satellite of claim 11, wherein the antenna array comprises four or more antenna elements.
 29. In a satellite communication system comprising: at least one LEO satellite of claim 1; and a plurality of terrestrial gateway devices, each terrestrial gateway device in communication with a plurality of terrestrial sensor devices; a method of communication between the at least one LEO satellite and the plurality of terrestrial gateway devices comprising: based on the orbital schedule data, the at least one processor dynamically reconfiguring the reconfigurable digital logic processing device to process signals received by the antenna array or to generate and transmit signals through the antenna array; the antenna array receiving signals and making the received signals available to the reconfigurable digital logic processing device; the reconfigurable digital logic processing device processing the received signals to amplify a subset of the received signals corresponding to signals transmitted by one or more of the plurality of terrestrial gateway devices, or the reconfigurable digital logic processing device making available to the antenna array signals for transmission in one or more transmission directions corresponding to respective locations of one or more of the plurality of terrestrial gateway devices.
 30. The method of claim 29, further comprising the communication sub-system processing the amplified subset of received signals to decode information encoded in the subset of received signals.
 31. The method of claim 29, further comprising the reconfigurable digital logic processing device processing the received signals to attenuate a second subset of the received signals corresponding to signals not of interest received by the antenna array.
 32. A method for providing a satellite communication service, comprising: providing a LEO satellite of claim 1 as a payload to a satellite launch vehicle.
 33. A method for providing a satellite communication service, comprising launching a satellite launch vehicle configured to release the LEO satellite of claim 1 for travel in a low earth orbit.
 34. The LEO satellite of claim 11, wherein the LEO satellite has a mass in the range of 10 kg to 50 kg.
 35. The LEO satellite of claim 11, wherein the chassis has a CubeSat structure and a size from 1 CubeSat unit to 50 CubeSat units.
 36. The LEO satellite of claim 34, wherein the chassis has a CubeSat structure and a size from 3 CubeSat units to 24 CubeSat units.
 37. The LEO satellite of claim 11, wherein the chassis comprises a major face, a minor face, the major face having a greater surface area than the minor face; and the antenna array is provided on at least a part of the minor face.
 38. The LEO satellite of claim 11, wherein the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to: process the signals received by the antenna array to attenuate transmissions received from one or more directions not of interest according to the orbital schedule of the LEO satellite, or attenuate signals to be transmitted by the antenna array in one or more directions not of interest for transmission according to the orbital schedule of the LEO satellite.
 39. The LEO satellite of claim 11, wherein the orbital schedule data comprises one or more antenna array configuration records, each antenna array configuration record comprising: an ephemeris record indicating a scheduled position of the LEO satellite in orbit over a period of time; and array factor coefficients associated with each of the two or more antenna elements defined in relation to the ephemeris record.
 40. The LEO satellite of claim 39, wherein each array factor coefficient is a complex number weight comprising a real coefficient value and an imaginary coefficient value.
 41. The LEO satellite of claim 39, wherein the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to process the signals received by the antenna array or amplify signals transmitted by the antenna array based on the scheduled position of the LEO satellite and the array factor coefficients as defined in the antenna array configuration record associated with the scheduled position of the LEO satellite.
 42. The LEO satellite of claim 11, further comprising an analog to digital converter for pre-processing signals before processing by the reconfigurable digital logic processing device.
 43. The LEO satellite of claim 11, further comprising a digital to analog converter for processing signals generated by the reconfigurable digital logic processing device for transmission by the antenna array.
 44. The LEO satellite of claim 11, further comprising a signal channeliser for channelising signals before processing by the reconfigurable digital logic processing device.
 45. The LEO satellite of claim 11, wherein the reconfigurable digital logic processing device comprises a Field Programmable Gate Array (FPGA).
 46. The LEO satellite of claim 11, wherein when the LEO satellite receives signals from more than one directions of interest, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to level amplitudes of signals received from the more than one directions of interest.
 47. The LEO satellite of claim 11, wherein when the LEO satellite transmits signals to multiple directions of interest, the at least one processor dynamically reconfigures the reconfigurable digital logic processing device to level amplitudes of signals transmitted to the multiple directions of interest.
 48. The LEO satellite of claim 11, further comprising one or more variable gain amplifiers (VGAs) in communication with the at least one processor, wherein when the LEO satellite receives signals from more than one directions of interest, the at least one processor configures the one or more VGAs to level amplitudes of signals received from the more than one directions of interest.
 49. The LEO satellite of claim 11, wherein the LEO satellite is a microsatellite.
 50. A method of communication between at least one LEO satellite and a plurality of terrestrial gateway devices in a satellite communication system, the satellite communication system comprising: at least one LEO satellite of claim 11; and one or more terrestrial gateway devices; the method of communication between the at least one LEO satellite and the one or more terrestrial gateway devices comprising: based on the orbital schedule data, the at least one processor dynamically reconfiguring the reconfigurable digital logic processing device to process signals received by the antenna array or to generate and transmit signals through the antenna array; the antenna array receiving signals and making the received signals available to the reconfigurable digital logic processing device; the reconfigurable digital logic processing device processing the received signals to amplify a subset of the received signals corresponding to signals transmitted by at least one of the one or more terrestrial gateway devices, or the reconfigurable digital logic processing device making available to the antenna array signals for transmission in one or more transmission directions corresponding to respective locations of at least one of the one or more terrestrial gateway devices.
 51. The method of claim 50, further comprising the communication sub-system processing the amplified subset of received signals to decode information encoded in the subset of received signals.
 52. The method of claim 50, further comprising the reconfigurable digital logic processing device processing the received signals to attenuate a second subset of the received signals corresponding to signals not of interest received by the antenna array.
 53. A method for providing a satellite communication service, comprising: providing a LEO satellite of claim 11 as a payload to a satellite launch vehicle.
 54. A method for providing a satellite communication service, comprising launching a satellite launch vehicle configured to release the LEO satellite of claim 11 for travel in a low earth orbit. 